ASP-Zacodovka

--- 1---
public class Student
    {
        [Key]
        public int StudentId { get; set; }

        [Display(Name = "Student Name")]
        [Column(TypeName = "nvarchar(100)")]
        public string StudentName { get; set; }

        [Display(Name = "Number in class")]
        [Column(TypeName = "int")]
        public int Number { get; set; }

        [Display(Name = "City")]
        [Column(TypeName = "nvarchar(100)")]
        public string City { get; set; }

        [Display(Name = "Day of yout birth: ")]
        [Column(TypeName = "date")]
        public DateTime BirthDate { get; set; }

        [Display(Name = "Student class")]
        public SchoolClass SchClass { get; set; }

    }

--- 2 ---

public class SchoolClass
    {
        [Key]
        public int ClassId { get; set; }

        [Display(Name = "Class name")]
        [Column(TypeName = "nvarchar(20)")]
        public string ClassName { get; set; }

        public List<Student> StudentList { get; set; }

        [NotMapped]
        [Display(Name = "Students count")]
        public int StudentCount { get; }

    }

---- 3 ----

 public class ApplicationDBContext : DbContext
    {
        public ApplicationDBContext(DbContextOptions<ApplicationDBContext> options)
            : base(options)
        {
        }

        public DbSet<Student> students { get; set; }
        public DbSet<SchoolClass> classes { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<SchoolClass>()
                .HasMany(stcl => stcl.StudentList)
                .WithOne(st => st.SchClass);
        }

--- 4 ---

..... appsetings.json....
"ConnectionStrings": {
    "SchoolDbStr": "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=SchoolDBTest;"
  }


--- 5 ----

.... Startup.cs -> void Configure()...
   services.AddDbContext<ApplicationDBContext>(dbContOp => dbContOp.UseSqlServer(Configuration.GetConnectionString("SchoolDbStr")));

-- 6 ---
... Package Manager Console ...

Add-Migration "ÏnitialCreate"
Update-Database


-- 7 --
... Custom Validation --
 public class NumberValidation : ValidationAttribute
    {
        private readonly int Max;

        public NumberValidation(int max)
        {
            this.Max = max;
        }
        public override bool IsValid(object value)
        {
            if (!(value is int))
            {
                return false;
            }
            int num = (int)value;
            if (num > Max)
            {
                return false;
            }
            return true;
        }
    }